Mechanical arms are used extensively in hospitals and clinics to conveniently mount and locate pieces of equipment where a medical professional may make the best use of the equipment. The mechanical arms allow the user to position a mounted piece of equipment for better access or to move it out of the way when not in use but still allow it to remain in a relative location. Mechanical arms may generally be mounted to a wall or a ceiling. The invention relates to ceiling mounted mechanical arms. Equipment, such as monitors, sensors, or other medical devices is mounted to one end. A number of arms are mounted between the ceiling and the equipment and a number of roller thrust bearings are used to enable the equipment to be moved and positioned relative to the ceiling. What is presented is an improved roller thrust bearing for positioning the arms of the mechanical arm assemblies.